Many communications systems rely on multi-phase frequency generation. For example, some modulation schemes, such as quadrature modulation (e.g., I/Q modulation and/or quadrature amplitude modulation (QAM)), phase modulation, and/or phase-shift keying (PSK) may use multiple phases to transmit data signals. Additionally, some systems (e.g., peripheral component interconnect express (PCIe)) may use multiple phases to achieve signal shaping and/or to multiply the frequency.
Several circuit architectures exist for producing multiple phases, including passive and active phase shifters, frequency dividers, delay locked loops (DLLs), and voltage-controlled oscillators (VCOs). However, these circuits include several lumped circuits or a single distributed circuit to produce the multiple phases. Furthermore, the DLL circuits have high phase noise and do not operate at a wide bandwidth.